Facilitating retransmission of data packets in a packet radio communication system by utilizing a feedback acknowledgment scheme

ABSTRACT

Apparatus, and an associated method, for a frame-formatted radio communication system. Coordination is provided between MAC and RLP layers of a sending station through use of apparatus embodied at the MAC layer of the sending station. Also, apparatus is provided at a receiving station to reduce the generation of RLP layer NAK during segmented RLP frame retransmissions.

This application is a continuation of, and claims priority to, U.S.patent application Ser. No. 10/612,477, entitled “Apparatus, AndAssociated Method, For Facilitating Retransmission Of Data Packets In APacket Radio Communications System That Utilizes A FeedbackAcknowledgment Scheme,” filed Jul. 2, 2003, hereby incorporated byreference herein as to its entirety.

The present invention relates generally to a radio communication system,such as an IS-2000-compliant cellular communication system, thatcommunicates frame-formatted, or other packet-formatted, data pursuantto a hybrid ARQ (HRAQ), or other, acknowledgment feedback andretransmission scheme. More particularly, the present invention relatesto apparatus, and an associated method, by which to coordinate packetretransmissions when the acknowledgment feedback and packet formattingschemes are carried out at multiple logical layers of the radiocommunication system. The present invention also more particularlyrelates to apparatus, and an associated method, by which better tocontrol generation of negative acknowledgment requests when data framesare retransmitted at data rates lower than at initial data transmissionrates.

Coordination between the logical layers is provided to permit earlierretransmission, when necessary, of a data frame. When an indication offailure of delivery of a data frame is detected at a lower-logicallayer, an indication of the failed delivery is provided to ahigh-logical level and the data retransmission commences. Multiple-layerfeedback acknowledgments are obviated. And, when retransmission of thedata frame occurs at a reduced data rate, a failed delivery indicationis less likely to be generated merely due to the reduced rate ofretransmission of the data frame. When implemented in a CDMA-2000cellular communication system that provides for reverse-link 1×EV-DVcommunication services, improved communications are provided. Bettercontrol of communication when segmented frames are retransmitted isprovided, and improved coordination between RLP and H-ARQretransmissions is provided.

BACKGROUND

Many aspects of modern society require the communication of datapursuant to the effectuation of communication services. And, the need tocommunicate data shall likely continue and perhaps increase asadvancements in communication technologies permit additional types ofcommunication services to be effectuated.

Data is communicated by way of a communication system. A communicationsystem includes, at a minimum, a set of communication stations includinga first communication station and a second communication station. Thecommunication stations are interconnected by way of a communicationchannel. Data is originated at a first of the communication stations,referred to as a sending station. The data is sent by the sendingstation upon the communication channel to be delivered to at least asecond of the communication stations, referred to as a receivingstation. The receiving station detects the data communicated thereto andoperates to recover the informational content thereof.

A radio communication system is a communication system that utilizesradio channels upon which to communicate data between the communicationstations. The radio channels are formed upon radio links defined upon aradio air interface. Wire line communication systems, in contrast,require a fixed, i.e., a wire line, connection between the communicationstations upon which to form communication channels that are permittingof the communication of data therebetween.

Radio communication systems provide various advantages that sometimesfavor their use over corresponding wire line communication systems. Thephysical infrastructure of a radio communication system, for instance,is generally relatively less costly to install than that of acorresponding wire line communication system. Initial deployment costsof a radio communication system, therefore, are generally less thanthose of corresponding wireline communication systems. Additionally, andsignificantly, a radio communication system can be implemented as amobile communication system. In a mobile communication system,communication mobility is provided. That is, one or more of thecommunication stations of a mobile communication system is mobile andnot limited to operation at a fixed position.

A cellular communication system is a type of mobile radio communicationsystem that has achieved significant levels of usage. The networks ofvarious cellular communication systems have been deployed to encompassmany populated portions of the world. Telephonic communications areprovided by way of the networks of cellular communication systemsthrough the use of mobile stations. That is, radio communications areeffectuated during operation of the cellular communication systembetween a network part of the communication system and a mobile stationto effectuate a communication service.

The area encompassed by the cellular communication system is defined bythe placement of fixed-site base transceiver stations. The basetransceiver stations each define a coverage area, referred to as a cell,and the aggregated areas of the cells defined by the coverage areas ofall of the base transceiver stations together define the areaencompassed by the system. The network part of the cellularcommunication system also includes control entities and entitiespermitting connection with other communication networks, such as PSTNs(public-switched, telephonic networks) or PDNs (packet data networks),such as the Internet.

A mobile station, when used to communicate data, usually communicateswith the base transceiver station positioned in closest proximity to themobile station. Viz., the mobile station communicates with the basetransceiver station that defines the cell in which the mobile station ispositioned.

Successive generations of cellular communication systems have beendeveloped and deployed. New-generation systems are being deployed andothers are under development. Certain of the new-generation systems arereferred to as being third-generation (3G) systems. In general, thesesystems are predicated at least in part upon packet-based communicationschemes. In a packet communication scheme, data that is to becommunicated is formatted into packets and the packet-formatted data iscommunicated in the form of a series of data packets to effectuate thecommunication of the data pursuant to a communication service. And,additional systems, sometimes referred to as successor-generationsystems, are also predicated at least in part upon packet-based, e.g.,frame-formatted, communication schemes.

The operating parameters are of an exemplary third generationcommunication system is set forth in an operating specification referredto as the CDMA 2000 operating specification. The operating parametersset forth in the CDMA 2000 operating specification provides for packetbased data communication services. Further operating parameters relatedto high speed data communication services have also been promulgated toprovide for the effectuation of high speed data communication servicesin the CDMA 2000 system. A 1×EV-DV data communication scheme, forexample, provides the operating parameters pursuant to which high speeddata communication services can be effectuated in conjunction with aCDMA 2000 communication system. High speed data communication servicesare effectuated in either direction, i.e., by the network part to amobile station as well as, also, by a mobile station to the networkpart.

Existing versions of the operating specification define thecommunication system in terms of logical layers, including an RLP (RadioLink Protocol) logical layer and an MAC (Medium Access Control) layer orsub-layer. RLP-formatted data packets, or frames, are formed at the RLPlayer, and MAC layer formatting is performed at the MAC layer. Bothlayers utilize a feedback acknowledgment scheme used to determinewhether to retransmit a data frame. The RLP layer utilizes a NAK-basedretransmission scheme and the MAC layer utilizes and H-ARQ scheme.

Additionally, the operating specification defines a reverse Packet Datachannel (R-PDCH). Two different types of transmissions are permitted onthis channel. First, autonomous transmission is defined. In autonomoustransmission, an “always on” data connection, minimally controlled, isprovided. When the mobile station operates pursuant to autonomoustransmission, the mobile station is permitted to communicate data at adata rate up to a predetermined data rate. Scheduled transmission isalso defined. In scheduled transmission, the network part, e.g., thebase station, determines when the mobile station is permitted totransmit at next higher rates from the autonomous transmission, up tothe peak data rate. In addition to the communication of relatively shortframe lengths, e.g., five or ten milliseconds, to improve the delayperformance of communications, hybrid ARQ (H-ARQ) feedback is alsoutilized for the reverse link to reduce the frame error rate due topower control inaccuracies.

For instance, any time in which the mobile station is to communicatedata, the mobile station is autonomously permitted to transmit at datarates up to a data rate, e.g., 9.6 kbps, specified during the callset-up procedures. For scheduled transmission, the mobile stationrequests permission to transmit, and the network part responds with agrant, including a rate assignment. The mobile station is then permittedto transmit the data during a permitted duration and at a permitted datarate.

Both autonomous and scheduled transmission uses the same type of H-ARQfeedback acknowledgment mechanism. The H-ARQ scheme exhibits theattributes of multiple ARQ “channels” and synchronous acknowledgment.Retransmissions of an encoder packet is performed up to a selectednumber of retransmissions. With the use of reverse link H-ARQprocedures, a symmetric H-ARQ mechanism is provided at the MAC sub-layerbetween the mobile station and the base transceiver station of thecommunication system.

One problem with the existing communication scheme set forth in theexisting version of the operating specification pertains to feedbackacknowledgments during retransmission of data packets or frames. AnRLP-formatted frame might first be communicated in non-segmented form ata high data rate and then retransmitted in segmented form at a lowerdata rate. When retransmitted at the lower data rate, a base transceiverstation forming a receiving station might indicate a failure of deliveryof the data due to timeout caused by its retransmission at a low datarate even through the retransmission of the data frame is ongoing.

Additionally, due to the multiple layers of feedback acknowledgments,excessive air resources are used to communicate the feedbackacknowledgments at the multiple layers. The multiple-layer feedback isduplicative and wasteful of radio resources.

If a manner could be provided by which better to provide control overthe retransmission of data pursuant to an acknowledgment feedback schemewould therefore be advantageous.

It is in light of this background information related to retransmissionof data in a packet communication system that the significantimprovements of the present invention have evolved.

SUMMARY

The present invention, accordingly, advantageously provides apparatus,and an associated method, for facilitating communication of packet datain a radio communication system, such as an IS-2000-compliant, cellularcommunication system. Frame-formatted, or other packet-formatted data iscommunicated pursuant to an H-ARQ, or other, acknowledgment andretransmission scheme.

Through operation of an embodiment of the present invention, a manner isprovided by which to coordinate frame retransmissions when theacknowledgment feedback and packet formatting schemes are carried out atmultiple logical layers of the radio communication system.

Also through operation of an embodiment of the present invention, amanner is provided by which better to control generation of negativeacknowledgment requests when data frames are retransmitted at data ratesare lower than at initial data transmission rates.

In one aspect of the present invention, coordination between the logicallayers is provided, and earlier retransmission, when necessary, of datais permitted. When an indication of failure of delivery of a data frameis detected at a lower logical layer, a message is formed thereat,forming an indication of the failed delivery. The message is provided toa higher logical layer level, and the data retransmission commences. Theneed otherwise to utilize otherwise multiple layer feedbackacknowledgments is obviated.

In another aspect of the present invention, failed delivery indicationsare less likely to be generated when the retransmission of data isperformed in segmented parts. That is to say, when non-segmented data isfirst transmitted and then retransmitted in segmented form at a reduceddata rate, a failed delivery indication is less likely to be returnedmerely due to the lowered rate at which the data is retransmitted. Falseindications of failure of delivery of data is less likely to occur,resulting in improved communication performance as well as betterutilization of radio resources in the communication system.

In an exemplary implementation, improved communications in a CDMA-2000,cellular communication system that provides for 1×EV-DV communicationservices are provided. Better control of communication is provided whensegmented frames are retransmitted. And, improved coordination betweenRLP and H-ARQ transmissions is provided.

Data formatting is performed at a higher logical layer, such as an RLP(Radio Link Protocol) layer and then provided to a lower logical layer,such as an MAC (Medium Access Control) sub-layer. MAC, or other, lowerlevel formatting is performed, and a resultant frame is communicated bya sending station to a receiving station. The communications at the MAC,or other, lower level logical layer are performed pursuant to a feedbackacknowledgment scheme, in particular, an H-ARQ feedback scheme.

H-ARQ indications of either successful transmission or failedtransmission are returned to the lower logical level of the sendingstation to be detected thereat. Responsive to detection of theindications by a detector embodied at the lower logical layer of thesending station, a status response generator generates a status responsemessage. The status response message is provided to the RLP, or other,upper logical level layer to indicate quickly the receive indications.When failed delivery of the data is indicated, the RLP, or other upper,logical layer commences retransmission procedures. The data is providedagain to the lower logical layer, and the data is retransmitted to thereceiving station.

The receiving station utilizes a retransmission timer for timing timeperiods associated with the delivery of data thereto. The datacommunicated by a sending station to the receiving station iscommunicated in autonomous or scheduled transmission modes. Theretransmission of the data might occur at a lower data rate than theinitial transmission of the data. When a determination is made at thereceiving station that data is received in segmented form, indicative ofretransmission at a lowered data rate, the segmented portions arebuffered at a resequencing buffer and a resequencing buffer timer isused to determine when to request subsequent retransmission of the data.If a segmented portion of the data is not detected in the time periodwithin which the resequencing buffer timer times-out, an NAK indicationis returned to the sending station to indicate the failed delivery ofthe segmented portion of the data. Accommodation is thereby made for theretransmission of the data at a lowered data rate. Unnecessary NAKindications indicating failed delivery of the data, assumingretransmission of the data at the lower transmission rate.

Thereby, improved communications and improved usage of radio resourcesis provided. Multi-level transmission of feedback acknowledgments atmultiple levels is obviated. And, erroneous indications of faileddelivery of retransmitted data is less likely to occur.

In these and other aspects, therefore, apparatus, and an associatedmethod, is provided for a radio communication system. The radiocommunication system has a sending station that sends data to areceiving station. The data is formatted at an upper-level logical layerand into an upper-level data frame. The upper-level data frame isprovided to a lower-level logical sub-layer. The upper-level data frameis further formatted thereat into at least one lower level frame. Thelower level logical layer is operable pursuant to an H-ARQ feedbackscheme. Retransmission by the sending station of the upper level dataframe is facilitated if the receiving station fails adequately toreceive the at least one lower level frame. An H-ARQ detector isembodied at the lower level logical sub-layer. The H-ARQ detectordetects H-ARQ indications, i.e. acknowledgement, returned by thereceiving station to the sending station. An H-ARQ status responsegenerator is embodied at the lower-level logical sub-layer. The responsegenerator is adapted to receive indications of detections made by theH-ARQ detector. The H-ARQ status response generator generates an H-ARQstatus response message for delivery to the upper-level logical layer.The message notifies the upper-level logical layer when the H-ARQdetector detects an H-ARQ indication indicating that the receivingstation fails adequately to receive the at least one lower-level frame.The upper-level logical layer is selectably operable responsive toreceipt of the H-ARQ status response message to provide again the upperlevel data frame to the lower level logical sub-layer.

Also in these, and other, aspects, further apparatus, and an associatedmethod, is provided for the radio communication system. The receivingstation comprises a retransmission timer. The retransmission timer timesa first time period commencing with at least anticipated reception atthe receiving station of the at least one lower-level frame. The sendingstation selectably initially sends the at least one lower-level frame insegmented portions at a second, reduced data rate. Reception of the atleast one lower level frame in the segmented portions is facilitated. Aretransmission timer resetter is adapted to receive indications ofdetection of reception of the segmented portions of retransmission ofthe lower-level frame at the second, reduced data rate. Theretransmission timer resetter causes resetting of the retransmissiontimer when the lower level frame is retransmitted in the segmentedportions.

A more complete appreciation of the present invention and the scopethereof can be obtained from the accompanying drawings that are brieflysummarized below, the detailed description of the presently preferredembodiments of the invention, and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a functional block diagram of a radio communicationsystem in which an embodiment of the present invention is operable.

FIG. 2 illustrates a logical layer representation of portions of theradio communication system shown in FIG. 1 and of signaling generatedduring operation of the radio communication system pursuant to operationof an embodiment of the present invention.

FIG. 3 illustrates a method flow diagram listing the method of operationof the method of an embodiment of the present invention.

FIG. 4 illustrates a representation of an exemplary relationship betweendata formatted at an RLP layer and at an MAC sub-layer of a sendingstation operable pursuant to an embodiment of the present invention.

FIG. 5 illustrates a representation of an exemplary transmission patternduring exemplary operation of the communication system shown in FIG. 1.

FIG. 6 illustrates a representation of exemplary communication ofsegmented portions of a data frame pursuant to operation of anembodiment of the present invention.

DETAILED DESCRIPTION

Referring first to FIG. 1, a radio communication system, shown generallyat 10, provides for the communication of frame-formatted, or otherpacket-formatted, data. The communication system forms a multi-usercommunication system having a plurality of mobile stations, of which themobile station is representative. Data is communicated pursuant toeffectuation of communication services, including, for instance, realtime VoIP (Voice over Internet Protocol) communication services.

In the exemplary implementation, the radio communication system forms acellular communication system that operates generally pursuant to theoperating protocol set forth in the CDMA 2000 operating specification.The communication system is also representative, however, of other typesof communication systems. While the following description shall describeexemplary operation of an embodiment of the present invention withrespect to its implementation in a CDMA 2000-compliant communicationsystem, in other implementations, embodiments of the present inventionare analogously implemented in other types of communication systems.

Data is communicated to effectuate communication services between anetwork part of the communication system and mobile stations operable inthe communication system. When data is communicated by the network partto a mobile station, the data is communicated upon forward link channelsdefined upon a forward link 16. And, when data is to be communicated bya mobile station to the network part, the data is communicated uponreverse link channels defined upon a reverse link 18.

The network part includes a radio access network, here shown to includebase transceiver stations, of which the base transceiver station (BTS)22 is representative the base transceiver stations are positioned atselected locations throughout an area, encompassed by the communicationsystem, and within which communications by, and to, a mobile station arepermitted. Each base transceiver station of the communication systemdefines a cell. And, a mobile station generally communicates with thebase transceiver station that defines the cell in which the mobilestation is positioned. The mobile station 12 and base transceiverstation 22 are, in general, representative of any set of communicationstations between which frame-formatted data is communicated during acommunication session to effectuate a communication service.

The CDMA 2000-compliant communication system forming the communicationsystem 10 here further provides for 1×EV-DV, high data ratecommunication services, both on the forward link as well as also on thereverse link. Exemplary operation of the communication system in whichdata, originated at the mobile station, is communicated to the basetransceiver station shall be described. In some aspects, analogousoperation for forward link communication are similarly implemented.

The radio access network of the network part of the communication systemalso includes a base station controller 24, or other control entity. Thebase station controller controls various aspects of the radio accessnetwork, including operation of the base transceiver station 22 to whichthe controller is coupled.

The base station controller 24, in turn, is coupled to a gateway (GWY)28 that forms a gateway between the radio access network of the networkpart of the communication system and other portions of the network part.Here, the gateway 28 connects the radio access network to a packet datanetwork (PDN) 32 and public switched telephonic network (PSTN) 34. Acorrespondent node (CN) 38 is coupled to the packet data network andpublic switched telephonic network. The correspondent node isrepresentative of any data source or target that forms the ultimatesource or destination of data communicated during a communicationsession to effectuate a communication service with, or by, a mobilestation, such as the mobile station 12.

Data originated, for instance, at the correspondent node forcommunication to the mobile station is routed through the network partof the communication system to the base transceiver station, and basetransceiver station transmits the data to the mobile station. And, forinstance, data originated at the mobile station for communication to thecorrespondent node, is sent upon reverse link channels to be detected bythe base transceiver station and, thereafter, to be routed through thenetwork part of the communication system to the correspondent node.

As mentioned previously, communication of data, such as pursuant to a1×EV-DV communication service, is frame-formatted, or otherwisepacket-formatted. That is to say, the communication service iseffectuated through the communication of successive frames of data. And,a feedback acknowledgment scheme is utilized by which feed back isprovided to indicate at least when frames of data are not successfullydelivered so that the data frame can be retransmitted.

During reverse link communications, data is communicated by the mobilestation upon reverse link channels to a base transceiver station. Framesof data are sent upon the reverse link channels to the base transceiverstation to be detected thereat. In the event that the data frame is notsuccessfully delivered to the base transceiver station, an indication ofthe failure of the delivery of the data frame is returned to the mobilestation pursuant to an H-ARQ feedback scheme. Because formatting andfeedback conventionally is performed at an RLP (Radio Link Protocol)layer and at a MAC (Medium Access Control) layer, multiple feedbacks,for each of the layers are returned to the mobile station.

The mobile station includes apparatus, shown generally at 46, thatfacilitates quick retransmission of data in the event of failed deliveryof a data frame to the base transceiver station. The apparatus 46 ishere shown to be formed of functional entities that are implemented inany desired manner, including, for instance, algorithms executable byprocessing circuitry. In the exemplary implementation, the apparatus isimplemented at a MAC (Medium Access Control) layer positioned beneath anRLP (Radio Link Protocol) logical layer.

Here, the apparatus 46 includes an H-ARQ detector 52 that operates todetect H-ARQ indications, indicating failed delivery of apreviously-sent data frame. Indications of the detection made by thedetector 52 are provided to an H-ARQ status response generator 54. Thestatus response generator, also embodied at the MAC layer together withthe H-ARQ detector, operates, in turn, to generate a message, hereindicated on the line 56, that is provided to the RLP layer to indicatethe failed delivery of the previously sent frame. When delivered to theRLP layer, the RLP-formatted frame is again provided to the MAC layer tobe formatted thereat and thereafter retransmitted to the basetransceiver station. Because the RLP layer is notified immediately ofthe detection at the MAC layer of the H-ARQ indication of faileddelivery, the RLP layer more quickly initiates retransmission of anRLP-formatted frame. The need otherwise to await delivery of an RLPlayer, NAK (negative acknowledgment) or other indication indicative offailed delivery of the frame is obviated. Improved communications arepossible as well as more efficient utilization of radio resourcesallocated to the radio communication system.

The base transceiver station also includes apparatus 46 of an embodimentof the present invention. The apparatus 46 embodied at the basetransceiver station also is formed of functional entities that areimplemented in any desired manner, also, for instance, by algorithmsexecutable by processing circuitry. The apparatus 46 operates duringreverse-link communications to control when feedback indications arereturned to the mobile station to indicate failed delivery of a dataframe. The apparatus detects when a retransmitted data frame istransmitted in segmented portions at reduced data rates, reducedrelative to a data rate at which the data is first transmitted.

A retransmission timer 58 embodied at the base transceiver station hasassociated therewith a first timeout. The retransmission timer operatesto initiate an NAK indication to be returned to the mobile station whena data frame is not successfully delivered within the time periodindicated by the first time out period. When, as described previously,retransmission of the data effectuated in segmented portions, theretransmission is carried out, sometimes at a much-reduced data rate.The apparatus includes a resequencing buffer 62 that buffers thesegmented portions of the data when the data is retransmitted duringoperation of the communication system. The apparatus also includes aretransmission timer resetter 64. The retransmission timer resetter iscoupled to receive indications of buffering at the buffer of a segmentedportion of a retransmitted data frame. And, the resetter is coupled tothe retransmission timer to cause resetting of the retransmission timerwhen a segmented portion of the retransmitted data is delivered to thebase transceiver station to be stored at the resequencing buffer. And,the apparatus also includes a resequencing buffer timer 66 that operatesto time a second time period. If the resequencing buffer timer times outand a segmented portion of the retransmitted data is not successfullydelivered to the base transceiver station, an indication is provided toa retransmission request generator 72 that initiates a retransmissionrequest, indicating the segmented portion, or portions, that are to beretransmitted to indicate to the mobile station that the missingsegmented portion, or portions, of the data frame must again beretransmitted to the base transceiver station. Because theretransmission timer is reset inappropriate generation of NAKindications indicating failed delivery of data, merely due toretransmission at a markedly lowered transmission rate does not occur.And, through the use of the resequencing buffer timer and retransmissionrequest generator, retransmission of segmented portions that aresuccessfully delivered to the base transceiver station are not resent.

FIG. 2 illustrates a representation of the mobile station 12 and basestation 22 that forms portions of the radio communication system shownin FIG. 1. Two of the logical layers, the RLP and MAC layers, indicatedat 76 and 78, respectively, are shown. And, the H-ARQ detector 52 andthe H-ARQ status response generator 54, used pursuant to reverse-linkcommunications, of the apparatus 46 are again shown to embodied at theMAC layer 78-12 of the mobile station.

FIG. 2 also illustrates an arrow 82 that represents the communication ofH-ARQ indications, such as from the base transceiver station to themobile station. And, communication of data between the layers of themobile and base stations are indicated by the arrows 84, andcommunication of acknowledgments and negative acknowledgments betweenthe layers is indicated by the segments 86. The message generated by theresponse generator 54 is indicated by the segment 86 extending betweenthe MAC and RLP layers of the mobile station. When the message isdelivered to the RLP layer, the RLP layer starts a subsequentretransmission at an earliest possible time. Through this operation,peer-to-peer RLP NAK control frames need not be communicated between thebase transceiver station and the mobile station.

Instead, at the MAC layer, the status of the H-ARQ transmission isprovided, and the indication, either of a successful transmission or anexhaustedly failed transmission is passed up to the RLP layer, i.e., theRLP transmitter. Once the transmitting RLP layer receives thetransmission failure indication, the RLP layer starts the retransmissionof the failed RLP frames immediately. In other words, the RLPretransmission is no longer triggered by a negative acknowledgment fromthe base transceiver station, the RLP receiver, but triggered by an NAKnotification formed at the transmitting MAC layer 78-12 directly.

At the transmitting side, i.e., here, the mobile station, in order forthe MAC to report the transmission status of the RLP frames, the RLPlayer indicates the RLP sequence numbers for RLP frames passed down tothe MAC sublayer. The MAC sublayer keeps track of the RLP sequencenumbers for all of the RLP frames that are encapsulated into a physicallayer SDU of each H-ARQ channel. That is to say, the MAC layerassociates each RLP sequence number with H-ARQ information, such asH-ARQ channel ID, subpacket ID, etc. The MAC sublayer then indicates thetransmission status of the RLP frames back to the RLP layer, aftereither receiving an ACK from the receiver or exhausting the allowableretransmission to complete the H-ARQ activity. With the H-ARQtransmission status indication from the MAC layer, the RLP layer 76-12starts the retransmission for the failed frames. The RLP layer alsoreleases the memory of the successful frames from a transmission bufferthereat. This increases not only the efficiency of the radio spectrumusage, i.e., much less or no more RLP NAK indications sent over theradio air interface, but also the throughput memory efficiency of thetransmitting station.

At the receiving side, i.e., here, the base transceiver station duringreverse link communications, the MAC layer and H-ARQ operations areunchanged. That is to say, normal H-ARQ ACK/NAK protocols are carriedout in traditional manner. However, at the RLP receiver, i.e., the RLPlayer 76-22, when an RLP frame is detected missing, RLP starts aDELAY_DETECTION_WINDOW timer or retransmission timer and waits for asubsequent round of retransmitted frame data before sending an NAKcontrol frame back to the transmitter. Since the transmitterautomatically start the retransmission of the failed frame, theretransmitted frame will arrive before the timer expires and NAK controlframe is sent from the receiver, less or no more RLP NAK frames back tothe transmitter over the air interface. The transmitter can beconfigured to stop sending the NAK control frame if the air link is goodand ACK/NAK in the H-ARQ is reliable.

FIG. 3 illustrates a method, shown generally at 92, representative ofthe transmission procedures carried out during communication of dataframes to effectuate a communication service.

First, and as indicated by the block 94, all RLP variables areinitialized at the transmitter, i.e., the mobile station for reverselink communications. Then, and as indicated by the decision block 96, adetermination is made whether the transmitter is active. If not, the nobranch is taken to the block 98 and operations stop. Otherwise, the yesbranch is taken to the block 102, and the RLP layer checks for data,either new or retransmitted data, ready for transmission. Higherpriority is given to retransmitted packets.

Then, and as indicated by the block 104, the RLP layer sends frames tothe MAC layer with their associated RLP sequence numbers (SEQ). For asegmented frame, the RLP layer also passes down a segment sequencenumber (S_SEQ) associated with each segmented portion.

At the decision block 106, a determination is made as to whether apacket in the H-ARQ channel has been acknowledged (ACKED). If so, theyes branch is taken to the block 108, and the transmission status isindicated with RLP sequence numbers and loop is taken back to thedecision block 96.

If, conversely, the no branch is taken from the decision block 106, theH-ARQ retransmission count is advanced, indicated by the block 112.Then, and as indicated by the decision block 114, a determination ismade as to whether H-ARQ retransmission is exhausted. If so, the yesbranch is taken to the block 108. If not, the no branch is taken back tothe block 104. Operations continue, as appropriate.

FIG. 4 illustrates the RLP layer 76-12 and the MAC sublayer 78-12 of themobile station 12. Here, the procedures that are carried out by themethod 92 are represented. The RLP layer passes down to the RLP frames116 and 118 to the MAC sublayer 78-12. The associated sequence numbersare also passed down. The MAC sublayer multiplexes both the RLP framesinto one physical channel SDU that later is coded for transmission.After the physical layer ARQ procedure, the MAC sublayer 78 notifies thedata instance (SR_ID=1), the transmission status of RLP frames withsequence numbers 3 and 4.

Thereby, in the RLP transmitter, i.e., the RLP layer 76-12 with thefeedback from the MAC sublayer, the RLP layer initiates a subsequentround of retransmission procedures without waiting for the NAK controlframes from the RLP receiver (the layer 76-22, shown in FIG. 2). Also,in the MAC transmitter 78-12, the MAC layer needs to keep track of theRLP sequence numbers of all of the data blocks that are multiplexed intoeach physical layer SDU. At the end of the transmission, the status ispassed up to the RLP layer. Primitives, i.e., requests and responsesbetween the MAC and RLP layers are as follows:

Primitive Primitive Type Primitive Parameters Used In Notes Request MAC-data, Mobile The RLP delivers an RLP to the MAC Data size, Stationsublayer to be multiplexed seq, and Base into physical layer SDU; s_seqStation Data is an RLP frame or a segment thereof, size is the size datain bits; seq is the sequence no. of the RLP frame containing data; s_seqis the segment sequence number if the RLP frame is a segmented frame.Request MAC- ack_or_nak, Mobile Indicates the transmission Data seqStation status of the RLP frame s_seq and Base transmitted on F-PDCH orR-ESCH; Station ack_or_nak is set to NAK to indicate the failedtransmission. seq is the sequence number of the RLP frame acked ornaked; s_seq is the segment sequence no. if the RLP frame is a segmentedframe.

FIG. 5 illustrates a representation, shown generally at 122, showingscheduled and autonomous transmission patterns during operation of theradio communication system shown in FIG. 1. Packet data transmissionpatterns in which packet data traffic is, generally, bursty, is shown.RLP frames are delivered in either segmented or non-segmented form. If alarge RLP frame is transmitted at a high data rate (scheduled)non-segmented is lost and the mobile station is unable to retransmit theRLP frame at the same data rate due to the base station load or raterequest delay, the retransmitted RLP frame can be transmitted in asegmented at autonomous mode. In the Figure, the blocks 124 representautonomous transmissions at a low data rate, and the blocks 126represent scheduled transmissions at a high data rate.

For instance, an RLP frame is, for example, transmitted at a peak datarate (1.2 Mbps) with a 10 ms frame length, but retransmitted at anautonomous mode, e.g. 192 bits per encoder packet, sixty-fourretransmissions would be required to retransmit the segmented datablock. An encoder packet subsequent to encoding also includes the inputbits on the forward/reverse packet data channel that consists of theinformation bits, the frame quality indicator bits, and tail bits. Thisforms a physical layer SDU. Normally, the RLP transmit timer set at around trip time plus a factor for processing delay period. If the roundtrip delay is 150 ms and a factor is 100 ms, the retransmit timer is 250ms. But, the time required to transmit the sixty-four segmented frameswith a 10 ms frame length is 640 ms. This causes the RLP receiver torequest a third round of RLP transmissions while the transmitter isstill conducting a segmented retransmission for the second round of RLPtransmission.

An effective retransmission scheme is required whenever theretransmitted frame is segmented due to an air resource limit.

FIG. 6 illustrates a representation of retransmission of data insegmented portions and operation of the apparatus of an embodiment ofthe present invention by which to limit unnecessary RLP NAK duringsegmented RLP frame retransmissions. The top portion of the Figureillustrates frames received at a resequencing buffer and the bottomportion of the Figure illustrates frames 134 received at asub-resequencing buffer.

When a segment of the retransmitted frame is received, an RLP receiver,the RLP layer 76-22 shown in FIG. 2, should stop the retransmissiontimer for the missing RLP frame and start a resequencing buffer, whichis used to resequence all segmented frames for the missing frame. Notethat a frame is segmented frame when a segmented data frame format isused. The NAK procedure for the subresequencing buffer is started and issimilar to that of the RLP resequencing buffer. In FIG. 6, the RLP framenumber 3, so, an NAK is sent for the retransmission. Before theretransmit timer expires, segmented subpacket 3-1 arrives. The subpacket3-1 is a segmented frame with S_SEQ field (segment sequence number) isset to zero. The receiver starts a subresequencing buffer to wait forthe rest of the segments. The segments 3-2 (S_SEQ=20), 3-4 (S_SEQ=60),and 3-5 (S_SEQ=80), etc. all arrive. But, the segment 3-3 fails toarrive (S_SEQ=40) upon the expiration of the delay detection window. TheRLP receiver then declares the missing segment 3-3 to be lost and an NAKcontrol frame is sent out to request retransmission for this segment.

Thereby a manner is provided by which to reduce the generation ofunnecessary RLP NAK indications.

The preferred descriptions are of the preferred examples forimplementing the invention, and the scope of the invention should notnecessarily be limited by this description. The scope of the presentinvention is defined by the following claims.

1. A method, comprising: receiving at a lower level protocol layer of atransmitter an upper-level data frame from an upper level protocol layerof the transmitter for transmission to a recipient; formatting theupper-level data frame into at least one lower-level frame in accordancewith a retransmission scheme; transmitting the at least one lower-levelframe to the recipient; determining at the lower level protocol layer ofthe transmitter that the at least one lower-level frame was notadequately received; generating a status message at the lower levelprotocol layer of the transmitter for notifying the upper level protocollayer of the transmitter that delivery of the at least one lower-levelframe was unsuccessful; and delivering the status message from the lowerlevel protocol layer of the transmitter to the upper level protocollayer of the transmitter.
 2. The method of claim 1, wherein determiningthat the at least one lower-level frame was not adequately receivedcomprises receiving a failed delivery indication at the lower levelprotocol layer of the transmitter in accordance with the retransmissionscheme.
 3. The method of claim 1, further comprising: receiving at thelower level protocol layer of the transmitter a portion of theupper-level data frame resent by the upper level protocol layer of thetransmitter; and retransmitting lower-level data frames corresponding tothe resent portion of the upper-level data frame to the recipient. 4.The method of claim 3, wherein the resent portion corresponds to the atleast one lower-level frame for which delivery was unsuccessful.
 5. Themethod of claim 3, wherein the data rate of the retransmission is lowerthan the data rate of the initial transmission of the at least onelower-level data frame to the recipient.
 6. The method of claim 1,wherein the retransmission scheme comprises a hybrid automatic repeatrequest (H-ARQ) feedback scheme.
 7. The method of claim 1, wherein thelower level protocol layer of the transmitter comprises a Medium AccessControl (MAC) layer in a mobile station, the MAC layer comprising ahybrid automatic repeat request (H-ARQ) detector and a H-ARQ statusresponse generator, and wherein the upper level protocol layer of thetransmitter comprises a radio link protocol (RLP) layer in the mobilestation.
 8. The method of claim 7, wherein the received upper-level dataframe comprises an RLP sequence number, and generating the statusmessage comprises embedding data corresponding to the RLP sequencenumber into the status message.
 9. An apparatus, comprising: circuitrythat implements an upper level protocol layer configured to send data toa recipient via a lower level protocol layer; and circuitry thatimplements a lower level protocol layer comprising a detector and astatus response generator, wherein the lower level protocol layer isconfigured to: receive a formatted data frame from the upper levelprotocol layer; reformat the formatted data frame into at least onelower-level frame in accordance with a retransmission scheme; transmitthe at least one lower-level frame to the recipient; determine that theat least one lower-level frame was not adequately received by therecipient; generate with the status response generator a status messagefor notifying the upper level protocol layer that delivery of theformatted data frame was unsuccessful; and deliver the status message tothe upper level protocol layer.
 10. The apparatus of claim 9, whereindetermining that the at least one lower-level frame was not adequatelyreceived by the recipient comprises receiving a failed deliveryindication in accordance with the retransmission scheme.
 11. Theapparatus of claim 9, wherein the lower level protocol layer is furtherconfigured to: receive a portion of the formatted data frame resent bythe upper level protocol layer; and retransmit lower-level framescorresponding to the resent portion of the formatted data frame to therecipient.
 12. The apparatus of claim 11, wherein the resent portioncorresponds to at least one lower-level frame for which delivery wasunsuccessful.
 13. The apparatus of claim 11, wherein a data transmissionrate associated with the retransmission is lower than a datatransmission rate associated with the initial transmission of the atleast one lower-level frame to the recipient.
 14. The apparatus of claim9, wherein the retransmission scheme comprises a hybrid automatic repeatrequest (H-ARQ) feedback scheme, the detector comprises a H-ARQdetector, and the status response generator comprises a H-ARQ statusresponse generator.
 15. The apparatus of claim 9, wherein the lowerlevel protocol layer comprises a Medium Access Control (MAC) layer in amobile station.
 16. The apparatus of claim 15, wherein the upper levelprotocol layer comprises a radio link protocol (RLP) layer in the mobilestation.
 17. The apparatus of claim 16, wherein the received formatteddata frame comprises an RLP sequence number, and wherein the lower levelprotocol layer is further configured to embed data corresponding to theRLP sequence number into the status message.
 18. An apparatus,comprising: a resequencing buffer configured to receive from a senderand store a plurality of lower-level data frames formatted in accordancewith a hybrid automatic repeat request (H-ARQ) feedback scheme; aretransmission timer configured to measure a period of time between thearrival of two sequential frames in the plurality of receivedlower-level data frames; and a retransmission request generatorconfigured to receive an indication that the retransmission timer hasreached a predetermined timeout period, and configured to generate anegative acknowledgement (NAK) message for transmission to the senderindicating that at least one lower-level data frame was not received bythe apparatus, wherein the apparatus is configured to receive at leastone of the plurality of lower-level data frames as a plurality ofsegmented frame portions, and wherein the apparatus further comprises: asub-resequencing buffer configured to receive and store a plurality ofsegmented frame portions corresponding to a lower-level data frame; anda resequencing buffer timer configured to measure a period of timebetween the arrival of two sequential segmented frame portions in theplurality of segmented frame portions corresponding to the lower-leveldata frame.
 19. The apparatus of claim 18, wherein the NAK messagecomprises a retransmission request including an identifier associatedwith at least one lower-level data frame that was not received by theapparatus.
 20. The apparatus of claim 18, wherein the retransmissionrequest generator is further configured to generate a NAK messagesubsequent to a timing out of the resequencing buffer timer, the NAKmessage indicating to the sender that a segmented frame portion was notreceived.
 21. The apparatus of claim 18, wherein the resequencing buffertimer is configured based on an expected data receiving rate that isless than an expected data receiving rate associated with theretransmission timer.
 22. The method of claim 1, wherein the transmittercomprises a mobile station and the lower level protocol layer comprisesa Medium Access Control (MAC) layer in the mobile station.
 23. Themethod of claim 22, wherein the upper level protocol layer comprises aradio link protocol (RLP) layer in the mobile station.
 24. The method ofclaim 2, wherein the failed delivery indication received at the lowerlevel of the transmitter does not correspond to a negativeacknowledgement (NAK) message received from a radio link protocol (RLP)layer of the recipient.
 25. The apparatus of claim 10, wherein thefailed delivery indication received at the lower level of thetransmitter does not correspond to a negative acknowledgement (NAK)message received from a radio link protocol (RLP) layer of therecipient.
 26. The apparatus of claim 19, wherein the NAK message isgenerated at a Medium Access Control (MAC) layer in the apparatus. 27.One or more non-transitory computer readable media storingcomputer-executable instructions which, when executed, cause anapparatus to: receive at a lower level protocol layer of the apparatus aformatted data frame from an upper level protocol layer of theapparatus; reformat the formatted data frame into at least onelower-level frame in accordance with a retransmission scheme; transmitthe at least one lower-level frame to a recipient; determine that the atleast one lower-level frame was not adequately received by therecipient; generate with a status response generator a status messagefor notifying the upper level protocol layer of the apparatus thatdelivery of the formatted data frame was unsuccessful; and deliver thestatus message to the upper level protocol layer.
 28. The computerreadable media of claim 27, wherein determining that the at least onelower-level frame was not adequately received by the recipient comprisesreceiving a failed delivery indication in accordance with theretransmission scheme.
 29. The computer readable media of claim 27,wherein the computer-executable instructions, when executed, furthercause the apparatus to: receive at the lower level protocol layer of theapparatus a portion of the formatted data frame resent by the upperlevel protocol layer of the apparatus; and retransmit lower-level framescorresponding to the resent portion of the formatted data frame to therecipient.
 30. The computer readable media of claim 29, wherein theresent portion corresponds to at least one lower-level frame for whichdelivery was unsuccessful.
 31. The computer readable media of claim 29,wherein a data transmission rate associated with the retransmission islower than a data transmission rate associated with the initialtransmission of the at least one lower-level frame to the recipient. 32.The computer readable media of claim 27, wherein the retransmissionscheme comprises a hybrid automatic repeat request (H-ARQ) feedbackscheme, and wherein the lower level protocol layer of the apparatuscomprises a H-ARQ detector and a H-ARQ status response generator. 33.The computer readable media of claim 27, wherein the lower levelprotocol layer of the apparatus comprises a Medium Access Control (MAC)layer.
 34. The computer readable media of claim 33, wherein the upperlevel protocol layer of the apparatus comprises a radio link protocol(RLP) layer.
 35. The computer readable media of claim 34, wherein thereceived formatted data frame comprises an RLP sequence number, andwherein the computer-executable instructions, when executed, furthercause the apparatus to: embed at the lower level protocol layer of theapparatus data corresponding to the RLP sequence number into the statusmessage.
 36. The computer readable media of claim 28, wherein the faileddelivery indication received at the lower level protocol layer of theapparatus does not correspond to a negative acknowledgement (NAK)message received from a radio link protocol (RLP) layer of therecipient.